The present invention relates generally to activated media. More particularly, the present invention relates to a method of stabilizing activated media and media produced thereby.
It is often desirable to impregnate, cover, or otherwise treat a base material with an active or activated material, such as an absorbent or adsorbent material. One example would be a non-woven medium coated with agents having fluid adsorption and/or odor adsorption characteristics, as found in children""s diapers, adult incontinence products, feminine hygiene products, and other adsorbent articles of clothing. Other examples include coated paper tissues and toweling, as well as surgical bandages and sanitary napkins. Other materials may be used as adsorbent materials, such as cyclodextrins or zeolites for odor control, or other adsorbents such as silicates, aluminas, or activated carbons.
The active, i.e., adsorbent, materials used to coat a base material may be fibrous or particulate materials. However, certain materials known in the art (e.g., fluff pulp fibers) have limited adsorption capacity, and hence perform disappointingly during normal wear. In addition, products containing such materials are often heavy and/or bulky. Thus, it is preferable to use at least some portion of particles composed of super adsorbent polymers (SAP).
Yet, it is difficult to immobilize powdered or small granular particles of SAP. Historically, microscopic active materials were immobilized on foams or on surfaces coated with a thin layer of pressure-sensitive adhesive. U.S. Pat. No. 5,462,538 to Korpman is an example of a method of immobilizing adsorbent material on a surface coated with a thin layer of pressure-sensitive adhesive. Using this method may produce large gaps between individual microscopic adsorbent elements. Also, the resulting adsorbent core has only a single layer of adsorbent material. PCT Publication No. WO 94/01069 to Palumbo is another example of a method of immobilizing particulate adsorbent material. However, the adsorbent particles are not bonded to the substrates. Moreover, the adsorbent particles are not in significant contact with the binder particles. Thus, neither method effectively restrains powdered or small granular particles of an active ingredient.
As a more effective alternative, U.S. Pat. No. 5,792,513, which is fully incorporated herein by reference, discloses a product formed from a composite mixture of adsorbent particles and binder particles fused to a substrate. While this product provides excellent absorption characteristics, the particles swell when exposed to fluid and then separate from the substrate and each other during normal use. This loose material is then free to slump or move.
In light of the foregoing, there remains a need for media, and a method of producing such media, in which the particles of an active ingredient are substantially immobilized even after they have become swollen, while maintaining excellent composite integrity.
The present invention provides an improved composite medium, in which the particles of an active ingredient are substantially immobilized. A further object is to provide absorbent or adsorbent articles having stabilizing particles dispersed throughout a coalesced composite layer of particles of an active ingredient and binder particles. By substantially immobilizing the particles of an active ingredient the present invention effectively prevents migration of the particles of an active ingredient, thereby creating an adsorbent product with enhanced integrity throughout the use cycle of the product.
Accordingly, the present invention provides composite media and a method of producing them. The composite media contain a coalesced composite mixture of particles of an active ingredient and binder particles. The binder particles preferably also fuse the composite structure to front and back substrates. The composite media also have stabilizing particles that fuse with both the particles of the active ingredient and the substrates, thereby forming a composite medium according to the present invention.